The present invention pertains to high purity zinc oxide powder and the manufacturing method thereof, a sputtering target obtained by firing this high purity zinc oxide powder, and a high purity zinc oxide thin film formed by sputtering this target.
Zinc oxide (ZnO) is white-colored powder, also known as zinc flower or zinc white, and is powder having hexagonal crystals.
Zinc oxide is used as white pigment for paint and artists' colors, and is also used as pharmaceuticals or cosmetics. Further, in recent years, zinc oxide is being used as a sputtering target material for forming thin films to be used in electronic components such as a semiconductor device.
Commercially available zinc oxide has a purity level of 95 to 99.9 wt %, and it is necessary to purify this further to obtain a purity level of 4N to 5N. In particular, C, Cl and S must be sufficiently reduced since these respectively form carbide, chloride and sulfide together with Zn.
As conventional technology, there is a method of collecting Zn from Zn-containing dust, and, with this method, Zn-containing dust containing Fe and Pb is leached with sulfuric acid solution, and subject to solvent extraction with D2EHPA. With this technology, although there is an effect in the removal of Fe, there is a problem in that Pb, Si and Al cannot be sufficiently removed (e.g., refer to Patent Documents 1 and 2).
Further disclosed is a wet generation method of zinc oxide for directly generating zinc oxide in a solution by neutralizing an aqueous solution containing zinc salt in antalkali (refer to Patent Document 3). Nevertheless, there is no particular description regarding the removal of C, Cl, S and Pb, and it is also speculated that this is accepting the existence of C, Cl, S and Pb.
Meanwhile, since high purity zinc having a purity level of 6N exists, it is also possible to consider oxidizing this to obtain high purity zinc oxide. Nevertheless, since this will become extremely costly, it is not realistic for industrial manufacture.    [Patent Document 1]    Japanese Patent Laid-Open Publication No. S59-116339    [Patent Document 2]    Japanese Patent Laid-Open Publication No. S59-126729    [Patent Document 3]    Japanese Patent Laid-Open Publication No. S53-116296